Generally, after a metal sheet has been cut from a metal coil to form a blank for a metal sheet, or cut from a blank to form a metal sheet, the metal sheet is stacked on top of one or more metal sheets for storage, shipping, and handling. When the metal sheets are stacked with one another, there is often minimal, if any, distance between the sheets (i.e., no gap). This lack of distance between the metal sheets results in difficulty in separating the sheets from one another. For example, robotic handling grips cannot insert any part of an end effector in between the sheets to then lift a sheet off of the stack. U.S. Pat. No. 3,440,988 describes the problems encountered in stacking flat metal sheets and forming non-structural deformations (i.e. dimples) to help prevent the metal sheets from stacking tightly.
EP0688614 discloses a method and apparatus for stamping a dimple into a sheet-metal blank to enable uniform stacking of the metal blanks. U.S. Pat. No. 5,673,585 discloses a punching or stamping apparatus for forming dimples in sheet metal such that no two dimples formed in subsequent blanks align when the blanks are stacked. Notwithstanding the above, there appears an absence of teaching to form dimples adjoining a cut edge and multiple sheets with staggered dimples along cut edges.
What is needed is a method for stacking metal sheets which allows the sheets to be easily removed from the stack. What is also needed is an apparatus which can create features in the metal sheets which allow for a gap to be formed in between the sheets when placed in a stack. What is needed is an apparatus which can off-set features, such as dimples, so as to avoid the features nesting with another to maintain the gap between the sheets when placed in a stack. What is needed is an apparatus which can create a plurality of dimples metal sheets in incrementally off-set locations to prevent nesting of the metal sheets.